Washington: In their most expensive ad war, the campaigns of President Barack Obama and Republican challenger Mitt Romney and their allies spent a record shattering USD 710 million in just 12 battleground states, according to a media report.

In the most heavily contested swing state of Ohio, the campaigns and the various ostensibly independent committees supporting them saturated the airwaves with USD 146 million worth of commercials on broadcast and local cable, CNN reported citing a source tracking ad buys.

Close behind Ohio were the two other swing states most heavily fought over: Florida, where USD 133 million worth of ad time was purchased and Virginia, which saw USD 110 million worth of commercials.

Six of the top 10 stations airing political ads were in Ohio: four in Cleveland and two in Columbus.

Several Republican super PACs, ostensibly independent political action committees that are by a federal court allowed to engage in unlimited political spending independently of the campaigns, bought air time in Pennsylvania during the final stretch hoping to put the state into play, CNN said.

The Obama campaign then countered resulting in a total of almost USD 26 million being spent there during the general election.

In the end the Obama campaign spent USD 260 million on their battleground ads while the Romney campaign purchased USD 180 million worth of commercials, it said.

When the campaign and its allies are combined Republicans with USD 411 million outpaced Democrats and their USD 301 million.